Powerful swells generated by Pacific storms battered California’s coastline, prompting pier closures, an evacuation warning, and concerns about flooding in coastal communities.

Northern California saw the most extreme conditions. According to National Weather Service Bay Area meteorologist Rachel Kennedy, waves exceeded 25 feet along much of the region’s coast, with localized heights of 50 to 60 feet at major surf breaks such as Mavericks in San Mateo County.

A buoy off Point Reyes recorded a wave height of 31.2 feet on Saturday morning—the highest recorded there since 2015, Kennedy said.

The surge was linked largely to storm activity across the Pacific, including a system near the Gulf of Alaska with hurricane-force winds. Those winds generated a powerful northwesterly swell that traveled toward California.

In communities including Pacifica and Half Moon Bay, footage showed waves breaking along the shoreline and pushing water onto streets. Witnesses described people being knocked over or scrambling away as particularly large waves came ashore.

Farther south, the Santa Cruz County Sheriff’s Office issued an evacuation warning for a section of coastline near Capitola.

Southern California also experienced hazardous surf. Manhattan Beach closed its pier Saturday morning after powerful waves crashed beneath the structure the previous afternoon.

National Weather Service forecasts for Los Angeles County called for waves of 6 to 9 feet on Saturday, increasing to 8 to 12 feet. Ventura County was expected to see similar conditions. Along the San Luis Obispo County coast, forecast wave heights ranged from 10 to 15 feet before building to 18 to 25 feet.

At the time of the report, Los Angeles County’s high surf advisory was scheduled to remain in effect until Tuesday afternoon, while a coastal flood advisory covered part of Saturday.

Officials urged visitors to stay away from exposed beaches and keep well back from the water when watching the surf. Kennedy emphasized that approaching the shoreline could endanger both spectators and rescuers.

Although the initial swell was beginning to weaken, forecasters expected additional northwesterly swells during the following week. Continued storm activity across the Pacific raised the possibility of further damaging surf along the coast.